As part of a growing effort to make America's cities more sustainable and to guarantee access to fresh and nutritious food for the urban poor, governments, non-profit organizations, community groups, and residents are looking to stimulate urban agriculture. Many gardens and small urban farms are located on vacant parcels in low-income areas where access to fresh produce and healthy food is limited, but the expansion of food production often is hindered by high concentrations of heavy metals and other contaminants in urban soils. In these cases, vegetables grown in these soils may therefore expose consumers to toxic levels of organic and inorganic pollutants. Despite the well-intentioned efforts of urban agriculture advocates to expand food production, no systematic study of soil contamination on vacant land has been conducted to date. If food production is to occur on vacant land in the post-industrial landscape of cities, basic research is needed in order to better understand the nature of such hazards and to warn the public from potential risks associated with the expansion of the very programs established to improve access to healthy food. The doctoral dissertation research project will integrate quantitative soil science and geospatial methods with theoretical insights from human geography (urban political ecology, environmental justice) to viability of using vacant land for food production in Oakland, California. The doctoral student will explore how historical patterns of investment and disinvestment have created an uneven urban landscape of food access and environmental quality, giving rise to both urban agriculture and the soil contamination that may hinder its expansion. The student also will analyze the spatial distribution of heavy metals (a material legacy of these patterns of investment) and whether or not concentrations pose a significant public health risk.
This project will contribute to basic scientific understanding of soil pollution and soil-quality management in urban agroecosystems, and it will illuminate the linkages between historical urban planning decisions and their material legacies. Because soil contamination and other such legacies continue to affect low-income neighborhoods, this project will help reveal how the "externalities" of economic growth and planning are ultimately "internalized" over time by the most economically disadvantaged (most often people of color). This research project will provide insights into the political and economic processes that have shaped urban zones of food insecurity and environmental pollution, and it will help the city of Oakland and community-based food justice organizations identify and assess the potential for vacant land to be used for urban agriculture. The project represents an application of the "precautionary principle" by assessing the risk of environmental contamination before urban farming projects are launched in order to ensure that sites are safe for food production. As a Doctoral Dissertation Research Improvement award, this award also will provide support to enable a promising student to establish a strong independent research career.
Urban agriculture has enjoyed renewed popularity across North America over the past few years due to a vibrant food justice movement challenging disparities in access to healthy food, as well as to municipal policy and planning efforts focusing on urban sustainability and public health. This NSF-funded dissertation research investigated the potential environmental hazards related to food production on urban soils and to identify potential sources of contamination. We evaluated the extent to which soil lead (Pb) contamination may be an obstacle to the expansion of urban agriculture in Oakland, California, by sampling soil at 110 potential urban agriculture sites throughout the city. We used a combination of GIS and spatial statistics to characterize the spatial distribution of Pb on vacant land at multiple scales across Oakland and to identify relationships between soil Pb levels and anthropogenic (human-caused) factors such as zoning, housing stock, roads, airport, and land use, as well as biophysical factors such as soil type, soil chemical characteristics, and vegetative cover. We also assessed the extent to which total soil Pb is actually available for plant uptake. Using samples collected in the field and two greenhouse experiments, we evaluated two chemical extractants (DTPA and MgCl2) in an effort to identify the best proxy for plant available Pb and to relate plant availability to a suite of soil chemical characteristics. While soil Pb levels were significantly higher in West Oakland and residential areas than other parts of the city, levels were generally lower than federal screening levels of 400 parts per million. Old housing stock (and lead paint) proved to be the primary anthropogenic factor affecting soil Pb levels, while soil phosphorus proved to be the most important chemical factor.
